A liquid crystal display device partially blocks light, by using a liquid crystal panel, emitted from a backlight device that is disposed on a rear-surface side of a liquid crystal cell, thereby forming an image on a front-surface side of the liquid crystal panel. The backlight device has a light source; a reflection portion disposed on a side opposite to the liquid crystal panel with respect to the light source; and a light diffusion portion that is disposed between the light source and the liquid crystal panel and diffuses light emitted from the light source and light reflected by the reflection portion.
In recent years, a liquid crystal display device that uses a large liquid crystal panel is widespread; and in the backlight device which uses a lamp as the light source, a plurality of lamps that are so arranged to be parallel with each other are employed. Besides, in the backlight device, the lamp is held by means of a member that is called a lamp holder.
A conventional liquid crystal display device is described in more detail with reference to drawings. FIG. 13 is a front view showing innards of a backlight device with a front portion of the liquid crystal display device omitted; FIG. 14 is a sectional view of the conventional liquid crystal display device.
The liquid crystal display device is formed by mounting a liquid crystal panel unit DP to a backlight device BL. As shown in FIG. 13, the liquid crystal display device is formed by combining the liquid crystal panel DP and the backlight device BL that has a shield 1; a reflection plate 2; a lamp 3; a lamp holder 95; and a diffusion plate 4. The lamp holder 95 has: a pair of lamp holders 951 that hold the lamp 3; a connection portion 952 from an upper surface of which the lamp holder 951 protrudes and to which the lamp holder 951 is connected; and an engagement portion 953 that is protruded from a lower surface of the connection portion 952.
The backlight device is assembled as described hereinafter. First, the reflection plate 2 is accurately positioned and disposed at a predetermined position of a bottom surface of the shield 1. At this time, holes (not shown) formed through the shield 1 and the reflection plate 2 lie on each other; the engagement portion 953 of the lamp holder 95 is inserted into and engaged with the through-hole, so that the lamp holder 95 is fixed to the shield 1.
The lamp 3 is held by the lamp holder 951 of the lamp holder 95 that is fixed to the shield 1. The lamp holder 951 has a cylindrical in which part of a circumferential side portion thereof is cut away; and the cut-away portion is formed upward. The width of the cut-away portion is widened and the lamp 3 is inserted; and the width of the cut-away portion is returned back to the original width, so that it is possible to surely hold the lamp 3.
On the other hand, the liquid crystal panel unit is formed by mounting and fixing the backlight device to a rear-surface side of the liquid crystal panel DP having a frame, so that the liquid crystal display device is formed. As shown in FIGS. 13, 14, in the backlight device, a plurality of lamps 3 are so arranged as to have an equal interval.
However, in a large liquid crystal display device, many lamps 3 are necessary to obtain sufficient brightness. If the number of lamps 3 increases, more electric power becomes necessary to turn on the lamps 3 and the amount of radiated heat increases. Because the amount of radiated heat increases, constituent members such as the reflection plate 2, the diffusion plate 4 and the like are changed in quality and deformed in some cases. Because of the quality change of the reflection plate 2, the diffusion plate 4 and the like, unevenness occurs in the light emitted from the rear surface of the liquid crystal panel DP, so that in some cases, a disadvantage sometimes occur, in which the quality of an image formed by the liquid crystal panel DP deteriorates.
To solve the disadvantages, as disclosed in JP-A-2004-287226, changing the disposition interval (pitch) of the lamp 3, which has been an equal interval so far, to an unequal pitch is proposed.
In a liquid crystal display device in which the lamps are disposed at an unequal pitch, the lamps 3 at the central portion are disposed at narrow intervals and the lamps 3 at the outsides are disposed at wide intervals. As described above, in a liquid crystal display device that uses a large liquid crystal panel, by changing the disposition pitch of the lamp 3 to an unequal pitch, it is possible to curb a dramatic increase in the consumed power and obtain sufficient brightness, and occurrence of brightness unevenness is reduced.    Patent document 1: JP-A-2005-203154    Patent document 1: JP-A-2004-287226